A motorist puts fuel in his carís gas tank. Ford said Thursday it will reduce gas mileage estimates for its C-Max hybrid, following a government investigation into consumer complaints that the carís actual mileage was lower.

DETROIT ó Ford will reduce gas mileage estimates for its C-Max hybrid, following a government investigation into consumer complaints that the carís actual mileage was lower, a person familiar with the matter said Thursday.

Ford will drop the combined city-highway mileage listed on the window sticker from 47 mpg to 43 mpg, according to the person, who asked not to be identified because the change has not been formally announced.

The U.S. Environmental Protection Agency, which monitors gas mileage testing, began its probe earlier this year after consumers complained that the C-Maxís mileage fell short of estimates.

Ford followed EPA methods to calculate the C-Max mileage, but in this case, the numbers still were overstated, according to the person familiar with the matter.

Ford spokesman Todd Nissen would not comment Thursday afternoon. The company had scheduled an announcement about gas-mileage on Friday, without giving specifics.

Itís the second time in less than a year that the EPA has made an automaker reduce window sticker mileage figures. In November, the EPA found inflated numbers on 13 Hyundai and Kia models.

The Ford error likely stems from EPA test procedures that let automakers test one car, then apply that carís gas mileage to other models with the same engines, transmissions and weight classifications, said John German, a senior fellow at the International Council on Clean Transportation and a former EPA mileage certification official.

In this case, Ford would be allowed to test the Fusion midsize hybrid and apply its mileage figures to the C-Max. But the C-Max may not get the mileage of the Fusion in the real world because it sits higher and has more wind drag.

The C-Max went on sale in October 2012. Through July of this year, the company had sold a total of 36,349. The C-Max starts at $25,200, which is nearly $9,000 more than its non-hybrid equivalent, the Ford Focus.

In the Hyundai-Kia case, the automakers acknowledged the problem with more than 900,000 vehicles. They changed the numbers and blamed a procedural error. As compensation, the companies have paid owners around $88 annually, based on the amount the mileage was overstated and the average price of gasoline. The customer payments are likely to cost the companies millions of dollars.

Automakers follow EPA procedures to test vehicles, and the EPA spot-checks their results or checks them in response to consumer complaints. But it rarely finds problems that warrant corrections. The EPA has said the Hyundai-Kia case was the first in which erroneous test results were found in so many models. Only two similar cases have been discovered since 2000, and those involved single models.

Some buyers refused to settle and sued in federal court, where Hyundai is now negotiating with plaintiffs. The EPA says itís still investigating the Hyundai-Kia case and could further punish the automakers.